Computer-aided design (CAD) software allows a user to construct and manipulate complex three-dimensional (3D) models. A number of different modeling techniques can be used to create a 3D model. These techniques include solid modeling, wire-frame modeling, and surface modeling. Solid modeling techniques provide for topological 3D models, where the 3D model is a collection of interconnected topological entities (e.g., vertices, edges, and faces). The topological entities have corresponding supporting geometrical entities (e.g., points, trimmed curves, and trimmed surfaces). The trimmed surfaces correspond to the topological faces bounded by the edges. Wire-frame modeling techniques, on the other hand, can be used to represent a model as a collection of simple 3D lines, whereas surface modeling can be used to represent a model as a collection of exterior surfaces. CAD systems may combine these and other modeling techniques, such as parametric modeling techniques. Parametric modeling techniques can be used to define various parameters for different features and components of a model, and to define relationships between those features and components based on relationships between the various parameters.
CAD systems may also support two-dimensional (2D) objects that are 2D representations of 3D objects. Two- and three-dimensional objects are useful during different stages of a design process. Three-dimensional representations of a model are commonly used to visualize a model in a physical context because the designer can manipulate the model in 3D space and can visualize the model from any conceivable viewpoint. Two-dimensional representations of a model are commonly used to prepare and formally document the design of a model.
A design engineer is a typical user of a 3D CAD system. The design engineer designs physical and aesthetic aspects of 3D models, and is skilled in 3D modeling techniques. The design engineer creates parts and may assemble the parts into a subassembly. A subassembly may also consist of other subassemblies. An assembly is designed using parts and subassemblies. Parts and subassemblies are hereinafter collectively referred to as components.
A design engineer or a manufacturing engineer may wish to view the internals of a CAD model. To do so, a section view of the model is constructed. A section view is a representation of a cross-section of the model and created by executing a Boolean cut operation on the model, essentially slicing through the model at locations defined by one or more planes. Defining and positioning the planes are a precursor to executing a Boolean cut operation.
Creating a cutting plane for a section view often requires a design engineer to employ sketch tools and techniques to draw a 2D shape that represents a cutting pattern. The design engineer thus needs to be trained how to use sketching tools and apply sketching techniques. In addition, sketching may require a significant amount of mouse travel and a significant number of mouse clicks to accomplish a task. SolidWorks® 2012 software, available from Dassault Systémes SolidWorks Corporation of Waltham, Mass., provides two section tools for creating a sketch in order to create a section view; thus, design engineers may need to learn how to use two different section tools, and also two different work flows.
Sketching a cutting pattern also requires the creation of geometric constraints, which typically involves selecting geometry in the sketch, selecting geometry in the 3D model, and selecting the type of constraint to apply (e.g., coincident or concentric). These tasks are repeated for each constraint to be added. Moreover, some constraints require the addition of one or more reference points that act as links between the sketch geometry and the 3D model geometry, each constrained to the reference point separately, forcing the sketch geometry to be constrained via an indirect connection to the 3D model geometry.
In general, state-of-the-art computerized modeling systems require the design engineer to constrain a line by the line's endpoints. For example, to constrain a line to the center of a hole so that the line passes through the center, the line is constructed as two lines, each having two endpoints. This is necessary to constrain the second endpoint of the first line and the first endpoint of the second line to the center of the hole because the line cannot be constrained at any point along the line.
Time-saving advantages can be obtained by not requiring a design engineer to create a sketch in order to create a section view. The overall goal of creating a section view is hindered by having to first create a sketch of the cutting pattern, during which time one or more points need to be manually constrained by the user, and projecting the sketch onto the model.
The length of time taken to generate a section view is a function of a number of factors, including how experienced the design engineer is with creating sketches, the number of constraints that need to be established, the number of different steps in the process (which may be determined by the number of mouse clicks), and the complexity of the desired section view.
To increase productivity, current state-of-the-art CAD systems would benefit from a system and method for providing a more intuitive work flow for creating a section view directly, without first having to create a sketch to help specify a desired section view. Providing a means to intuitively create a section view of a model and thereby reduce the amount of time to create the section view would enhance the capabilities of a computerized modeling system.